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                        <h1 id="string&#x65B9;&#x6CD5;">String&#x65B9;&#x6CD5;</h1>
<pre><code>            var num1 = &quot;123456,hello-js!&quot;;

            console.log(num1[0])                                // &#x53D6;&#x4E0B;&#x6807;
            console.log(&quot;charAt&quot;,num1.charAt(0))                // &#x8FD4;&#x56DE;&#x4E0B;&#x6807;&#x5BF9;&#x5E94;&#x5B57;&#x7B26;
            console.log(&quot;charCodeAt&quot;,num1.charCodeAt(9))        // charCodeAt &#x8FD4;&#x56DE;10&#x8FDB;&#x5236;&#x7684;unicode&#x7F16;&#x7801;&#xFF08;16&#x8FDB;&#x5236;&#xFF09;

            /**
             * indexOf &#x8FD4;&#x56DE;&#x5B57;&#x7B26;&#x4E32;&#x7247;&#x6BB5;&#x5F00;&#x59CB;&#x4F4D;&#x7F6E;&#x7684;&#x4E0B;&#x6807;&#xFF0C;&#x82E5;&#x4E0D;&#x5B58;&#x5728;&#xFF0C;&#x5219;&#x8FD4;&#x56DE;-1;
             *              &#x53EA;&#x4F1A;&#x8FD4;&#x56DE;&#x7247;&#x6BB5;&#x7B2C;&#x4E00;&#x6B21;&#x51FA;&#x73B0;&#x7684;&#x4F4D;&#x7F6E;;
             *               &#x7B2C;&#x4E8C;&#x4E2A;&#x53C2;&#x6570;&#x8868;&#x793A;&#x641C;&#x7D22;&#x7684;&#x8D77;&#x59CB;&#x4F4D;&#x7F6E;;
             * */ 
            console.log(&quot;indexOf&quot;,num1.indexOf(&quot;l&quot;,10))    
            console.log(&quot;lastIndexOf&quot;,num1.lastIndexOf(&quot;l&quot;,9))    // lastIndexOf &#x8FD4;&#x56DE;&#x6700;&#x540E;&#x4E00;&#x6B21;&#x51FA;&#x73B0;&#x7684;&#x4F4D;&#x7F6E;

            console.log(&quot;concat&quot;,num1.concat(&quot;!&quot;))                // concat &#x62FC;&#x63A5;&#xFF0C;&#x8FD4;&#x56DE;&#x7684;&#x662F;&#x65B0;&#x7684;&#x5B57;&#x7B26;&#x4E32;
//            num1 += &quot;!&quot; + &quot;?&quot;;

            console.log(&quot;fromCharCode&quot;,String.fromCharCode(104,101))    // &#x8FD4;&#x56DE;10&#x8FDB;&#x5236;unicode&#x7F16;&#x7801;&#x5BF9;&#x5E94;&#x7684;&#x5B57;&#x7B26;&#x4E32;

            /**
             *  slice(&#x5F00;&#x59CB;,&#x7ED3;&#x675F;) &#x622A;&#x53D6;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x7247;&#x6BB5;
             *             &#x5F00;&#x59CB;&#x4F4D;&#x5FC5;&#x9009;&#xFF0C;&#x652F;&#x6301;&#x8D1F;&#x6570;
             *             &#x7ED3;&#x675F;&#x4F4D;&#x53EF;&#x9009;&#xFF1A;&#x5982;&#x679C;&#x4E0D;&#x5199;&#xFF0C;&#x5219;&#x5230;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x6700;&#x540E;&#xFF0C;&#x652F;&#x6301;&#x8D1F;&#x6570;&#xFF08;&#x8868;&#x793A;&#x5012;&#x6570;&#x7B2C;&#x51E0;&#x4F4D;&#xFF09;
             * */
            console.log(&quot;slice&quot;,num1.slice(2,-1))                

            /**&#x529F;&#x80FD;&#x90FD;&#x662F;&#x83B7;&#x53D6;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x7247;&#x6BB5;
             * &#x7B2C;&#x4E8C;&#x4E2A;&#x53C2;&#x6570;
             * substr&#xFF1A;&#x957F;&#x5EA6;
             * substring&#xFF1A;&#x4E0B;&#x6807;&#x4F4D;&#x7F6E;&#xFF08;&#x4E0D;&#x5305;&#x542B;&#x81EA;&#x5DF1;&#xFF09;
             * */
            console.log(&quot;substr&quot;,num1.substr(1,2))                // [1,2]
            console.log(&quot;substring&quot;,num1.substring(1,2))        // [1,2)

            /**
             *  &#x5C06;&#x5B57;&#x7B26;&#x4E32;&#x4EE5;&#x67D0;&#x4E2A;&#x5B57;&#x7B26;&#x4E32;&#x4F5C;&#x4E3A;&#x5206;&#x5272;&#x70B9;&#x53BB;&#x5206;&#x5272;&#x4E3A;&#x6570;&#x636E;
             * */
            var data = &quot;0123456789&quot;;
            console.log(data.split(&quot;&quot;,4))                        // &#x7B2C;&#x4E8C;&#x4E2A;&#x53C2;&#x6570;&#x53EF;&#x4EE5;&#x9650;&#x5236;&#x6570;&#x7EC4;&#x7684;&#x957F;&#x5EA6;

            console.log(&quot;split&quot;,num1.split(&quot;-&quot;))
            // &#x591A;&#x4E2A;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x62FC;&#x63A5;
            var arr = [&quot;123456,hello&quot;,&quot;js!&quot;].concat([&quot;!!&quot;]);
            console.log(arr)
            // &#x5206;&#x5272;&#x53D8;&#x6570;&#x7EC4;&#x540E;&#xFF0C;&#x518D;&#x6B21;&#x7EC4;&#x88C5;&#x6210;&#x5B57;&#x7B26;&#x4E32;
            var str3 = &quot;&quot;;
            for(var i = 0; i &lt; arr.length; i++){
                str3 += arr[i];
            }
            console.log(str3)

            // &#x66FF;&#x6362; replace
            var str4 = &quot;&#x4ECA;&#x5929;&#x662F;&#x661F;&#x671F;&#x5929;&#x5417;&#x5929;&#x5417;&#x5929;&#x5417;&#x5929;&#x5417;&#x5929;&#xFF1F;&quot;;
            console.log(str4.replace(&quot;&#x5929;&quot;,&quot;&#x65E5;&quot;))
            // &#x7EC3;&#x4E60;&#xFF1A;&#x66FF;&#x6362;&#x6240;&#x6709;&#x7684;&quot;&#x5929;&quot;&#x5B57;
            function myReplace(str){
                for(var j = 0; j &lt; str.length; j++){    // &#x5FAA;&#x73AF;&#x6B21;&#x6570;&#x4E3A;str4&#x7684;&#x957F;&#x5EA6;
                    if(str.indexOf(&quot;&#x5929;&quot;) == -1){
                        console.log(j + &quot;&#x6B21;&#x6570;&quot;)
                        // &#x8DF3;&#x51FA;&#x5FAA;&#x73AF;
                        break;
                    }
                    str = str.replace(&quot;&#x5929;&quot;,&quot;&#x65E5;&quot;)
                }
                console.log(str)
                return str;
            }
            myReplace(str4);

            // &#x6B63;&#x5219;&#x8868;&#x8FBE;&#x5F0F;&#x5168;&#x5C40;&#x66FF;&#x6362;
            console.log( str4.replace(/&#x5929;/g,&quot;&#x65E5;&quot;) )        

            var str5 = &quot;hello&quot;;
            var str6 = &quot;HTML&quot;;
            console.log(&quot;toUpperCase&#x5927;&#x5199;&#xFF1A;&quot;,str5.toUpperCase())
            console.log(&quot;toLowerCase&#x5C0F;&#x5199;&#xFF1A;&quot;,str6.toLowerCase())

            // trim() &#x5220;&#x9664;&#x524D;&#x540E;&#x7A7A;&#x683C;
            var str7 = &quot;    &#x809A;&#x5B50;   &#x997F;&#x4E86;      &quot;
            console.log(&quot;trim&quot;,str7.trim().length)
</code></pre>
                    
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